The function of Ensembl gene identifier ENSG00000138079 (SLC3A1, solute carrier family 3 member 1) is as follows. Acts as a chaperone that facilitates biogenesis and trafficking of functional transporter heteromers to the plasma membrane (By similarity) (PubMed:10588648, PubMed:11318953, PubMed:16609684, PubMed:16825196, PubMed:32494597, PubMed:32817565, PubMed:7686906, PubMed:8486766, PubMed:8663184, PubMed:8663357). Associates with SLC7A9 to form a functional transporter complex that mediates the electrogenic exchange between cationic amino acids and neutral amino acids, with a stoichiometry of 1:1. SLC7A9-SLC3A1 transporter has system b(0,+)-like activity with high affinity for extracellular cationic amino acids and L-cystine and lower affinity for intracellular neutral amino acids. Substrate exchange is driven by high concentration of intracellular neutral amino acids and the intracellular reduction of L-cystine to L- cysteine. SLC7A9-SLC3A1 acts as a major transporter for reabsorption of L-cystine and dibasic amino acids across the brush border membrane in early proximal tubules (PubMed:10588648, PubMed:11318953, PubMed:16609684, PubMed:16825196, PubMed:32494597, PubMed:32817565, PubMed:7686906, PubMed:8486766, PubMed:8663184, PubMed:8663357). Associates with SLC7A13 to form a functional complex that transports anionic and neutral amino acids via exchange or facilitated diffusion. SLC7A13-SLC3A1 may act as a major transporter for L-cystine in late proximal tubules, ensuring its reabsorption from the luminal fluid in exchange for cytosolic L-glutamate or L-aspartate (By similarity). {ECO:0000250|UniProtKB:Q91WV7, ECO:0000269|PubMed:10588648, ECO:0000269|PubMed:11318953, ECO:0000269|PubMed:16609684, ECO:0000269|PubMed:16825196, ECO:0000269|PubMed:32494597, ECO:0000269|PubMed:32817565, ECO:0000269|PubMed:7686906, ECO:0000269|PubMed:8486766, ECO:0000269|PubMed:8663184, ECO:0000269|PubMed:8663357}.